While it's not a social media platform of any kind, I know Apple News has some of their main user-facing pages actively curated by humans they've hired directly

While it's not a social media platform of any kind, I know Apple News has some of their main user-facing pages actively curated by humans they've hired directly from editorial positions at various traditional media outlets. I thought it was an interesting idea when it started. I'm not sure how much of a real impact that's had, though.